Spacecraft propulsion/Talk

I heard that solar sails are propelled by photons hitting the 'sails'. But photons have no mass and therefore no momentum, so in a collision they provide no impulse? -- sodium

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What about future methods like matter-antimatter propulsion? --mike dill

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Photons have no rest mass. Photons have energy, however, so their "mass" is E/c**2, so their momentum is E/c. This momentum is imparted to the sail upon impact. - RjLesch.

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It may be interesting to note that if you make the sail reflect the photons, you actually get 2E/c per photon. --BlackGriffen --- yes the photons do provide the impulse to the sails. According to the Planetary Society who have built the first solar sail powered craft 99% of its propulsion should come from reflecting photons, only 1% from the solar wind. See also http://www.physlink.com/ae270.cfm and http://www.u3p.net/tipe/phot_jp.htm --rmhermen --- I added a description of other future methods that I've read about. I also marked them as future methods. rgvandewalker?

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WRT fusion rockets, would it be more accurate to say that we can't make a fusion reaction self-sustaining? We can sustain one, it just doesn't generate as much energy as we put in? Also, it might be worth mentioning some of the different schemes for using fusion power (ie Orion project with fusion bombs etc.) I also don't know whether classifying fusion rockets with antimatter drives and space warps is fair . . . we're likely to be able to do controlled fusion well before either of the others. Another possibility you haven't mentioned was powering sunsails with ground-based or satellite-based lasers Robert Merkel

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I'm moving warp drive to this page, because I don't think there's really much solid theory behind it; if there is, please add it (or online references to reputable sources). Otherwise, maybe it'd be worthwhile to set up a fictional spacecraft propulsion page?

Warp drives

No one knows how to grab space in order to warp it. It might be possible with extremely odd materials like neutronium, strange matter, or negative mass, but no one knows how to get these.

Warping space is easy, matter does it all the times (we call it gravity). The trick is finding a way to make a propulsion system out of it. --BlackGriffen

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Does a vernier rocket fit in to any of the categroies already listed? Just curious. Also, may I suggest a division of the rockets by category (i.e. chemical, ionic, other).--BlackGriffen

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A vernier is a steering rocket. Typically they will use one of the schemes already listed, usually a monopropellant. Hydrazine is popular.

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Text under "Nuclear Kinetic" read "Bimini Atoll". Changed to "Bikini Atoll" If this is wrong please change back.

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What does lemonade? have to do with Zubrin?'s magsail??